Spatial Dissociation Between Atrial Exit and the Putative Slow Pathway Substrate in Atypical AVNRT

BACKGROUND: Atypical atrioventricular nodal reentrant tachycardia (AVNRT) is characterized by heterogeneous reentrant circuits, and substrate-oriented ablation targets remain incompletely defined because retrograde slow pathway atrial exits are spatially variable. OBJECTIVE: This study aimed to explore the spatial relationship between sinus rhythm high-peak frequency (PF) regions and retrograde slow pathway atrial exits in atypical AVNRT and to evaluate the feasibility of a substrate-oriented ablation approach. METHODS: 11 patients with atypical AVNRT (8 fast-slow, 3 slow-slow) underwent catheter ablation guided by PF mapping during sinus rhythm. High-PF sites along the tricuspid annulus and atrial earliest activation sites during retrograde slow pathway conduction were mapped. Ablation was initially performed at the high-PF region, with additional atrial exit ablation when required. RESULTS: High-PF sites were identified in all patients, most commonly near the 5-o'clock tricuspid annular position. No patient demonstrated spatial concordance between the high-PF and atrial earliest activation sites (mean distance 10.9 ± 4.1 mm). Ablation at the high-PF region alone eliminated retrograde slow pathway conduction in 9 of 11 patients (82%). Additional atrial exit ablation was required in 2 patients. Acute success was achieved in all patients, with no recurrences for 6 months. CONCLUSION: In atypical AVNRT, atrial exits were frequently spatially dissociated from a putative slow pathway substrate identified during sinus rhythm. These findings provide hypothesis-generating mechanistic insight and suggest that sinus rhythm high-PF mapping may represent a feasible substrate-oriented approach warranting validation in larger controlled studies.